1. Field of the Invention
The present invention relates to an image processing apparatus and, more particularly, to the adjustment of a streaming amount in panning shooting using image composition.
2. Description of the Related Art
Panning is one of shooting techniques for expressing a sense of speed of a moving subject. Such a technique is directed to performing shooting such that panning a camera according to the movement of a moving subject results in a still picture in which the moving subject appears stationary and the background appears streaming. General panning shooting is performed while adjusting the shutter speed to a relatively slower value according to the moving speed of a subject to be shot (a main subject). However, since the shutter speed is set slower, even a main subject is likely to become a blurred image due to a camera shake or a difference between the moving speed of the main object and the speed of panning. In view of the above issues, it is desirable to simplify panning shooting by using an image processing technique.
For example, Japanese Patent Application Laid-Open No. 2012-094984 discusses an image capturing apparatus (an image pickup apparatus, an imaging apparatus) that captures a relatively low-sensitivity image and a relatively high-sensitivity image and combines a partial image corresponding to a main subject region in the relatively high-sensitivity image with the relatively low-sensitivity image. Japanese Patent Application Laid-Open No. 2010-166304 discusses an image capturing apparatus that sets a main subject region within an imaging region, performs a plurality of exposures in the set main subject region during a period in which one exposure is performed in a region different from the set main subject region, i.e., a background region, and combines images obtained at the respective exposures.
However, in the image capturing apparatus discussed in Japanese Patent Application Laid-Open No. 2012-094984, since the stream of the background is expressed with a single image, if the main subject is not accurately tracked, even when the main subject region in the relatively high-sensitivity image is combined with the relatively low-sensitivity image, a main subject in the low-sensitivity image may remain around the main subject region in the relatively high-sensitivity image. Also, since the main subject and the background are shot at respective different points of time, the shape of the main subject may change between two images, so that main subject regions in the two images may not accurately overlap each other.
Also, in the image capturing apparatus discussed in Japanese Patent Application Laid-Open No. 2010-166304, a main subject region is previously set and the stream of the background is expressed with a single image. Therefore, when the main subject goes out of the main subject region during shooting or when the background comes into the main subject region during shooting, the boundary between the main subject and the background may appear unnatural.